The invention is based on an apparatus for removing solid particles from internal combustion engine exhaust gases as disclosed hereinafter. In a known apparatus designed for this purpose, i.e., U.S. Pat. No. 4,478,613 there are a bundle of tubes, into each of which an electrode support is coaxially introduced, with electrode discharge disks being lined up quite close together on the electrode support. At the front end the tubes are exposed to exhaust gas, which flows longitudinally through the tubes and is discharged into a collecting chamber, from whence it is carried via a connecting line to a cyclone precipitator.
In the tubes, the soot which initially is very finely distributed is supposed to be charged by means of a corona discharge and to precipitate out on the walls of the tubes. As soon as large flakes or soot particles have accumulated on the walls and the layer of soot has grown to a predetermined thickness, the layer breaks off in flake-like pieces, and the resultant large soot flakes are carried along by the flow of exhaust gas and transported to the cyclone precipitator, where they are mechanically filtered out by centrifugal force. The known apparatus thus operates with a relatively low exhaust gas flow speed inside the tubes. In particular, according to proposals made in the known apparatus, the layer of soot is also supposed to be loosened with the aid of mechanical means, such as shaking or blowing devices. This occasions relatively great expense, and furthermore the apparatus occupies a great deal of space, so that in motor vehicles, especially passenger vehicles, operated with internal combustion engines the emissions of which are supposed to be kept free of soot components in particular, the apparatus is difficult to accommodate.
A further problem in the known apparatus is that the insulation, by way of which the supports are connected to the apparatus housing such that they are resistant to high-voltage and by way of which the supply of voltage from a high-voltage source is effected, experiences the flow of exhaust gas directly, especially the exhaust gas containing soot components in the form of large flakes, so the insulator surface rapidly becomes soiled. This soiling causes a considerable decrease in shunt resistance, so a considerable amount of energy can travel via the soot layer toward the housing during operation, greatly increasing the power requirements of the high-voltage system. Since the high-voltage system must be supplied by the engine with which the motor vehicle is being driven, the relative fuel consumption for such motor vehicles also increases to a marked extent, because of the power drawn for the high-voltage system. In the known apparatus, discontinuous operation may also occur, because soot components are periodically deposited on the tube walls and are then periodically removed, causing periodically increasing and decreasing amounts of soot to be filtered and possibly causing temporary overloading of the cyclone precipitator. Especially in cases where the soot that has been filtered out is returned to the intake side of the engine, so as to be afterburned there together with the fresh mixture, this kind of pulsating recirculation has a negative effect on the operation of the engine, especially on the result of combustion.